The statements in this section merely provide background information related to the present disclosure and do not necessarily constitute prior art.
A distributed antenna system (DAS) includes a head-end that is linked to signals of a plurality of base stations and a plurality of remote units (RUs) that is installed in an actual service area of the head-end. When a DAS with a single sector configuration is installed in highly populated areas such as a department store or a stadium, it might cause slowdown or interruption of a data service or call block of a voice service due to an excessive number of users. A DAS system supporting sectorization can prevent these problems by dividing the area served by a plurality of physical RUs into a plurality of sectors, and providing each sector with a signal among several different base station signals. Furthermore, a crowded location shifts depending on time windows and circumstances, and in some cases, two or more sectors are provided with a signal from the same base station. Rather than having fixedly divided sectors, adaptive sectorization technology is to adaptively link base station signals to different sectors, depending on time windows and circumstances.
Such technology is described in, for example, U.S. Pat. No. 8,913,892.
FIG. 1 is a block diagram of a DAS for supporting a sectorization. As shown in FIG. 1, a sectorization supporting device 100 includes a RIM (Radio Interface Module) unit 110, a RIM distribution matrix unit 120, an OIM (Optical Interface Module) distribution matrix unit 130, an OIM unit 140 and a RAU (Remote Access Unit) 150.
The RIM unit 110 receives downlink signals from base stations, separates a desired signal from the downlink signals by way of a filter, adjusts a power level of each separated signal, and distributes to the sectors which wants the separated signals.
The RIM distribution matrix unit 120 distributes the signals for the sectors, respectively. A signal to be distributed to a sector can be selected by a radio frequency (RF) switch located on each path for distributing the signals to the desired number Q of the sectors by the RIM unit 110. An output signal for each sector from the RIM distribution matrix unit 120 is inputted to the OIM distribution matrix unit 130 which may be included in the OIM unit 140.
The OIM distribution matrix unit 130 receives the sector-specific output signals from the RIM distribution matrix unit 120, and distributes received signals to the OIM unit 140.
The OIM unit 140 selects one of the sector-specific signals received from the OIM distribution matrix unit 130, converts the selected sector signal into an optical signal, and transmits the optical signal to the RAU 150.
The RAU 150 transmits an uplink optical signal to the OIM unit 140.
The OIM unit 140 converts the optical signal into an RF signal, and transmits the RF signal to the OIM distribution matrix unit 130 through a selected sector path.
The OIM distribution matrix unit 130 transmits a signal coupled for each sector to the RIM distribution matrix unit 120, and the RIM distribution matrix unit 120 transmits the sector-specific signal to each of a plurality of the RIM units 110. Each of the RIM units 110 selects a sector, receives a sector signal from the desired sector, filters the received sector signal, and transmits the filtered sector signal to the base station.
According to the system shown in FIG. 1, the RIM unit 110 includes a circuit for distributing base station signals to a plurality of sectors, and hence the number of sectors to be supported by a single RIM unit 110 ranges from 1 to N. In this case, the RIM unit 110 is designed to support N sectors, or redesigned to match another specified number of sectors less than N in order to minimize the number of unused paths.
For example, if the RIM unit 110 rated to support up to eight sectors utilizes only three sectors, five paths remain unused. This leaves unnecessary circuits for supporting the five extra paths to the disadvantage of the RIM unit 110 in terms of cost, size, and power consumption. In addition, where no adaptive sectorization is needed, it suffices that the RIM unit 110 supports only one sector, requiring none of a distribution circuit, an RF switch, an isolator, and the like for supporting the sectorization; however, the very presence of the circuits for supporting the eight sectors becomes redundant.
In the above-illustrated example, the RIM unit 110 requires circuits for distributing sector-specific signals regardless of whether there is a need for an adaptive sectorization. Further, utilizing a single RIM unit 110 designed to support a plurality of sectors occasionally results in excess sector-specific distributing circuits to no purpose. In order to minimize unused sector-specific distributing circuits, multiple RIM units 110 should be developed to meet the exact number of sectors to support, multiplied by the number of types of RIM units 110 depending on supported frequencies, resulting in a very wide range of RIM models to produce and manage according to the variety of sectors and frequency bandwidths.